Last summer, I took up canning. In my striving to eatbothlocallyandseasonally, I have been buying produce in bulk when it is at its cheapest, and transforming it to enjoy through the winter. U-Pick cherries have been made into frozen cherries and cherry butter. $2/lb blueberries are now pints of blueberry butter and quarts of spirited blueberries. Excess sungold tomatoes from my garden have been transformed into a pint of preserves (if you haven’t tried tomato preserves on a grilled cheese sandwich, you must remedy that situation ASAP).

Why do I can?

Because it allows me to eat locally all year long. Because it means I will be able to bring back the flavor and feeling of summer on a snowy December day. Because it gives me full control over the amount of sugar added to the preserves. Because I can season my preserves however I want , giving me more flavor options than I would find at the co-op.

Want to do some canning yourself? You will need:

Canning jars (necessary). Use jars specifically made for canning to ensure you can get a proper seal. You will be able to reuse the jars once you’ve eaten up the preserves. I use our jars for bulkfoods, refrigerating leftovers, or more canning. Just be sure to get a new lid if you reuse a jar for canning — the seals along the edges of the flat lids only work once!

A deep stockpot (necessary). For your jars to be shelf-stable (ie: the unopened jars will last a few months in your pantry), you need to use the boiling water canning method. Older recipes suggest inverting the jars to create a seal, but the USDA no longer regards this as safe: DON’T DO IT! The Ball preserving site has a greattutorial!

Note: If you are canning vegetables or other low-acid foods, including pumpkins, you MUST use a pressure cooker and an approved recipe. The boiling water method will not be sufficient to knock out all the potentially dangerous microbes!

A rack to keep the jars off the bottom of the stockpot (necessary). Boiling water needs to be able to surround the jars from all sides, including the bottom, in order for your preserves to be safe. Special canning pots come with a rack, but you can also rig something up yourself.

Jar lifter or tongs (necessary). You need something to lift the jars out of boiling water, right? A jar lifter will only set you back about $8, and is better suited for the size of the jars, but regular tongs with rubber bands on the end (to keep the metal from scratching the glass jars) will work as well.

At the beginning of last summer, I wanted to give canning a try, but I hesitated. I was afraid that I would somehow poison myself and my husband by doing it wrong. I’ve heard from several others that this is a concern, and I’ve done a lot of reading/research on the science end of it. I am much more confident now that my canned goods are going to be safe for my pantry. Phew!

Spoiling

As frightening as it may seem, microorganisms such as yeasts, molds and bacteria are naturally present in all foods. A natural level of these microorganisms will not harm us, but when left unchecked, these yeasts, molds and bacteria can grow, change, and multiply to poisonous or even toxic levels.

A less dangerous form of spoilage is quality loss. The canned food may be off-color or lose flavor.

Before using any canned food, check for these signs of spoilage. If any are present, throw it out!

● Bad odors

● Lid that bulges out

● Lid that comes off easily/doesn’t have a tight seal

● Mold

● Air bubbles moving towards the top (stationary air bubbles are fine…you just didn’t get them all out before you sealed the jar!)

The Three Factors

There are three things that can cause canned goods to spoil:

Microorganisms can grow.

Quality of food can drop because of enzyme activity. Enzymes are proteins that speed up chemical reactions, and occur naturally in all fruits and vegetables.

Recontamination due to outside air getting into the jars.

Beating the Big Three

Luckily, we can prevent all three of these factors from becoming an issue by properly canning our food.

For all canned vegetables that aren’t being pickled, a pressure cooker is absolutely necessary to insure safe food. For now, let’s focus on acidic foods such as pickles, jams, and fruit preserves. Do NOT use this science to can carrots, green beans, etc.

Savvy Tip: These methods will be safe for canned tomato products, as long as you add some lemon juice or other acid. Tomatoes are right on the border of foods safe to can using the boiling-water method, so make sure you add the amount of acid called for in the tomato recipe, and you’ll be good to go!

Most canned foods contain enough water to support microorganism growth, but by heating the food and adjusting the oxygen content and pH (acidity) of the food, we can keep problems at bay.

Heating

Heating food to 212*F (the boiling point of water) will kill most molds and yeasts, as well as some bacteria. It will also deactivate most of the enzymes that would otherwise hurt the quality of the food.

Savvy Tip: Older canning recipes may instruct you to simply invert the jars, rather than processing them in boiling water. However, this is no longer considered safe by modern food safety standards! As a result, a boiling-water canner should be used to process all jars of fruit preserves and pickles.